Effect of Current Density and Oxidation Time on Microstructure and Corrosion Resistance of Micro-Arc Oxidation Coatings on an Aluminum-Copper-Magnesium Alloy

Abstract Microstructural and corrosion resistance studies were conducted after micro-arc oxidation coatings were created at different current densities and oxidation periods to improve the corrosion resistance of Al-Cu-Mg aluminum alloy 2A12 (EN AW-2024). The effects of current density and oxidation time on the microstructure, elemental composition, phase composition, and corrosion resistance of the coating were investigated using SEM, EDS, XRD, white light interferometer, and electrochemical workstation analysis. The findings show that α-Al₂O₃ and γ-Al₂O₃ phases make up the majority of the coatings. Surface roughness progressively rises as the oxidation current density rises, layer thickness initially rises and then falls, and the self-corrosion current density essentially stays constant. As the oxidation duration grows, the film layer’s thickness progressively rises, the surface roughness first rises before stabilizing, and the self-corrosion current density dramatically drops. At a current density of 4 A/dm 2 and an oxidation time of 30 min, the film demonstrates optimal corrosion resistance, with a self-corrosion current density i corr of 3.15 × 10 -8 A/cm 2 , suggesting a considerable improvement in the film’s corrosion resistance.